The organic EL device is a light-emitting device utilizing electroluminescence of an organic compound. That is to say, the organic EL device comprises a pixel electrode, an opposite electrode and an organic emitting layer with electroluminescence function arranged between both electrodes. The material of organic luminescent layer with electroluminescence is classified into an organic polymer materials and a combination of low-molecular organic compounds (host material and dopant material). Examples of an electroluminescent organic polymer material include polyphenylene vinylene referred to as PPV and derivatives thereof.
A study of an organic emitting layer using organic polymer material as a material is currently conducted intensively, since it can be driven at a relatively low voltage, is low in the power consumption and is easy to comply with a large display screen of using an organic EL device. In addition, the organic emitting layer made of a organic polymer material as can be manufactured by a coating method such as an ink-jet method. Thus, productivity of the organic polymer EL device is significantly higher than the low-molecular organic EL device which uses a vacuum process.
The organic polymer EL display typically has a hole-injection layer arranged between the pixel electrode and the organic emitting layer in order to inject holes from the pixel electrode into the organic emitting layer efficiently. As the material of the hole-injection layer, oxides of the transition metal such as molybdenum oxide, tungsten oxide, vanadium oxide or the like are used (refer to, for example, Patent Documents 1-6).
In the case of the display panel using an organic polymer EL device, the material of an organic emitting layer (an organic polymer EL material) is arranged in each pixel according to the color (R, G or B) using a printing technology such as inkjet technology. Therefore, when printing with the ink containing the organic polymer EL material, it is necessary to prevent ink from intruding into neighboring pixel emitting light of the other color.
In order to prevent ink containing the organic polymer EL material from intruding into the neighboring pixels emitting light of the other color, there is a technology to provide a liquid repellent bank defining each pixel and dropping ink containing the organic polymer EL material exactly to each pixel in order to prevent the ink from intruding into the neighboring pixels (for example, refer to Patent Documents 7-12). In addition, to prevent the ink from flowing out from the area defined by the bank, there is known a technology to make the bank liquid repellent by treating the bank with UV light or plasma (refer to Patent Documents 9-12).
On the other hand, there is known a method to transform the surface property selectively by radiating the light to the organic thin film formed on the surface of the material (refer to, for example, Patent Document 13). These organic thin films whose property can be selectively transformed by the light radiation is in some cases referred to as “a self-assembly-monolayer (SAM)”. For example, a self-assembly-monolayer (SAM) is known, in which the contact angle of water on the surface can be changed by the changing the molecular structure through the irradiation.
In addition, to improve affinity of the pixel electrode with the liquid material of the organic functional layer to be coated, a technology is known to form a metal oxide layer containing the transparent electrode material such as ITO on the surface of the pixel electrode (refer to, for example, Patent Document 14).
In addition, a technology is known to increase the work function of the anode surface by applying the oxidation treatment on the anode surface (refer to, for example, Patent Document 15).